exam-scores-solution.py

A_boundary = -1
B_boundary = -1
C_boundary = -1
D_boundary = -1

while D_boundary < 0 or D_boundary > 1:
    D_boundary = float(raw_input("Enter the minimum percentage required for a 'D' (must be between 0 and 1): "))
    if (D_boundary < 0) or D_boundary > 1:
        print 'Sorry, the boundary of', D_boundary, "for a grade of 'D' is invalid.",
        print "Please try again."

while C_boundary <= D_boundary or C_boundary > 1:
    prompt = "Enter the minimum percentage required for a 'C' (must be between %f and 1): " % D_boundary
    C_boundary = float(raw_input(prompt))
    if (C_boundary <= D_boundary) or C_boundary > 1:
        print 'Sorry, the boundary of', C_boundary, "for a grade of 'C' is invalid.",
        print "Please try again."

while B_boundary <= C_boundary or B_boundary > 1:
    prompt = "Enter the minimum percentage required for a 'B' (must be between %f and 1): " % C_boundary
    B_boundary = float(raw_input(prompt))
    if (B_boundary <= C_boundary) or B_boundary > 1:
        print 'Sorry, the boundary of', B_boundary, "for a grade of 'B' is invalid.",
        print "Please try again."

while A_boundary <= B_boundary or A_boundary > 1:
    prompt = "Enter the minimum percentage required for an 'A' (must be between %f and 1): " % B_boundary
    A_boundary = float(raw_input(prompt))
    if (A_boundary <= B_boundary) or A_boundary > 1:
        print 'Sorry, the boundary of', A_boundary, "for a grade of 'A' is invalid.",
        print "Please try again."
        
score1 = -1
while score1 < 0 or score1 > 100:
    score1 = float(raw_input('Enter the score for exam 1: '))
    if score1 < 0 or score1 > 100:
        print 'The score must be between 0 and 100.  Please re-enter'

score2 = -1
while score2 < 0 or score2 > 100:
    score2 = float(raw_input('Enter the score for exam 2: '))
    if score2 < 0 or score2 > 100:
        print 'The score must be between 0 and 100.  Please re-enter'

score3 = -1
while score3 < 0 or score3 > 100:
    score3 = float(raw_input('Enter the score for exam 3: '))
    if score3 < 0 or score3 > 100:
        print 'The score must be between 0 and 100.  Please re-enter'

#  Compute the average score and put it into a variable named average_score
average_score = (score1 + score2 + score3) / 3
average_score_as_percent = average_score / 100

if average_score_as_percent >= A_boundary:
    grade = 'A'
elif average_score_as_percent >= B_boundary:
    grade = 'B'
elif average_score_as_percent >= C_boundary:
    grade = 'C'
elif average_score_as_percent >= D_boundary:
    grade = 'D'
else:
    grade = 'F'

print "Your average score was", average_score, 'for a grade of', grade